The present invention is directed to an expansion dowel assembly made up of an axially extending dowel body and an expansion member in contacting engagement with the dowel body and with an extension part on the expansion member and contacting the dowel body.
Expansion dowel assemblies of the general type mentioned above exhibit an after-expansion characteristic in use, that is, additional expansion occurs if a load is applied to the dowel body after the assembly has been set in a borehole. As a result, such dowel assemblies are often utilized for dynamic loads.
The expansion member must be capable of axial displacement relative to the dowel body so that after-expansion can take place, however, such relative movement is not always possible in known expansion dowel assemblies. Due to the development of excessively high surface pressures, the expansion member can become seized with the dowel body with the effect that in practice the expansion member is cold-welded with the dowel body. Excessively high surface pressures are produced when non-uniform distribution of the expansion pressure occurs and primarily such pressures are developed at the front end of the expansion member. If the expansion member becomes seized with the dowel body, in effect, it bites into the surface of the dowel body and further relative displacement of the expansion member and the dowel body is impossible. Providing the expansion member with a fillet radius, chamfering or the like can not solve the problem and leads to increased costs in fabrication.